Are vaccinated measles cases protected against severe disease?

We aimed to estimate vaccine effectiveness against severe measles based on the number of vaccine doses administered and the time since last vaccination.

We included measles cases aged at least 2 years and born since 1980 who were notified in France between 2006 and mid-2019. We considered two severity levels (moderate, severe) and calculated adjusted relative risks (aRR) using multinomial logistic regression.

We included 10,399 cases. The risk of severe measles in two-dose vaccine recipients was 71% (aRR = 0.29 [95%CI 0.12-0.72]) and 83% (aRR = 0.17 [95%CI 0.04-0.70]) lower than in unvaccinated cases, if the time since last dose was less or more than 15 years, respectively. The risk of moderate disease followed a similar pattern.

Two-dose measles vaccination provided long-term protection against severe cases, even after vaccine failures. These findings underscore the need for compliance to the recommended measles vaccination schedule to prevent severe cases.